This invention relates to new and improved piezoelectric sintered bodies of the lead calcium titanate type.
Articles by Y. Yamashita, K. Tokoyama et al, Japan. J. Appl. Phys. 20, Suppl. 20-4, 183 (1981), Y. Yamashita, S. Yoshida et al, Proc. FMA 4, Kyoto, Japan, 25 (1983) and S. Jyomura et al, J. Appl. Phys. 52, 4472 (1981) disclose sintered lead titanate piezoelectric ceramics exhibit characteristics making these useful for ceramic ultrasonic transducers. However, the piezoelectric ceramics disclosed in these references while showing properties that render these materials useful in some aspects exhibit other properties that make these materials less useful for use in ultrasonic transducers and for similar uses.
While the Yamashita et al 1981 article shows piezoelectric compositions exhibiting a relatively high thickness mode coupling (k.sub.t) to planar mode coupling (k.sub.p) ratio, it has been found that the piezoelectric constant (d.sub.33) is not sufficiently high for some purposes.
It is highly desirable for many purposes that the piezoelectric constant d.sub.33 be increased as far as possible while the ratio of k.sub.t /k.sub.p be maintained as high as possible. Additionally, it is also desired that the dielectric constant K be maintained as high as possible while the dissipation factor D be maintained as low as possible.